The invention relates to a vertical position fixing of a treatment chamber inside a tire vulcanizing machine for the fastening of treatment chamber elements at least during a vulcanization process so that in the closed position at least one defined vertical distance H can be fixed, wherein fixing means are provided on at least one treatment chamber element and designed in such a way that a fixing which is releasable and absorbs the occurring forces is facilitated.
The production of a tire, for example for vehicles such as automobiles or motorcycles, is an extremely costly process, consisting of a large number of production and process steps. The cause for this is the complicated tire construction which consists of a considerable number of different individual components. Added to this is the fact that this large number of components, under the effect of pressure and temperature of the so-called vulcanization, have to be interlinked. The vulcanizing process is also significant with regard to the material properties and adhesion properties of the finished tire.
For this reason, one of the essential production steps for producing tires is the vulcanizing of tire blanks culminating in a finished tire. To this end, the tire blank is inserted into a mold or tire mold which is located inside a tire vulcanizing machine and then heated to the material-dependent vulcanizing temperature and then subjected to the application of a vulcanizing pressure inside the tire blank. In order to reach the vulcanizing temperature and the vulcanizing pressure, a suitable heating medium at a corresponding temperature and under the application of pressure is introduced into the interior space of the tire blank.
The vulcanization basically has the aim of practically “finish baking” a tire blank by means of temperature and pressure application within one or more time intervals, that is to say to interlink the components of the tire blank and to impress elastic properties into the base materials and the India rubber/natural rubber layer by crosslinking processes. To this end, in addition to the actual pressure and temperature application different additive substances, matched to the base material, are furthermore required for the crosslinking and, if necessary, for the crosslinking acceleration.
For carrying out a vulcanization of the elastomer material, an appreciable amount of thermal energy has to be introduced into the material. To this end, it is largely insufficient to subject the tire blank to be vulcanized to the application of a vulcanizing temperature and a vulcanizing pressure on the inner side.
In order to achieve the amount of thermal energy and pressure application which are necessary for the vulcanization process, a pressure and/or temperature action upon the tire blank is alternatively or additionally provided on the outer side of the tire blank in the vulcanizing machine. To this end, a treatment chamber, which encompasses a tire mold and can be opened or closed, is usually installed so that the tire blank to be vulcanized can be inserted, vulcanized and removed.
Particularly thick regions of the tire blank are the treads. The sidewalls are of relatively thin design. The reason for this noticeable thickness difference are the additional tire components which are arranged in the region of the tread, such as steel breakers, breaker cover ply and the considerably thicker India rubber/natural rubber layer in comparison to the sidewall. This considerably thicker India rubber/natural rubber layer has a greater wall thickness not least because it encompasses the actual tire profile which is produced during the vulcanizing process. To this end, the tread region or the thick-walled India rubber/natural rubber mass provided there has to be heated until it can flow plastically and can be pressed by the vulcanization pressure into the profile-negative die of the tire blank mold of the tire vulcanizing machine. The plastic flowability increases with increased heating of the material within a wide range so that less pressing pressure is required in order to be able to reliably produce the profiling.
On account of the necessary vulcanizing temperatures of up to 200 degrees Celsius, frequently in the region of about 160 degrees Celsius, an appreciable temperature gradient exists inside the treatment chamber or the tire mold between the machine interior and the environment of the tire vulcanizing machine which usually has room temperature. This situation, in addition to the basic requirement of the machine operation, taking into account the most energy-efficient conservation of resources, is responsible for heat losses having to be reduced, especially as a result of convection over the surface of the treatment chamber of the tire vulcanizing machine.
Many tire vulcanizing machines are constructed in such a way that the treatment chamber is a functional core element. The treatment chamber serves either directly for accommodating the tire blank to be vulcanized or a tire mold or a so-called container and is delimited in its spatial extent by means of a bottom plate with mold pressure plate and a mold counter-pressure plate and also a preferably cylindrical tension casing. All the chamber delimiting components of the treatment chamber participate in the heat losses chiefly as a result of convection. The tension casing in particular with its considerably large surface causes large heat losses in this case.
Not only the convection-inducted heat losses have direct influence upon the energy balance of the tire vulcanizing machine. The size and especially the spatial volume of the treatment chamber is also a not inconsiderable factor in this respect. In the ideal case, the treatment chamber is dimensioned in such a way that the tire blank to be vulcanized in each case with or without an optionally encasing container or a tire mold can be accommodated. In this case, attention has to be paid to the fact that the treatment chamber has to be able to be opened and closed. Also, a handling space has to be facilitated, at least in the open position, in order to ensure the handling of the tire blanks or finished tires during unloading and loading of the treatment chamber.
In order to be able to carry out the tire vulcanization in an energetically favorable and functionally practical manner, especially in the case of alternately differently dimensioned tires, it is necessary that at least the height of the treatment chamber and/or its clear width can be influenced and adapted by means of suitable measures.
A further requirement criterion for the treatment chamber is the internal and/or external pressure application of the tire blank to be vulcanized. In order to achieve the amount of thermal energy and pressure application required for the vulcanization process, a pressure and/or temperature action upon the tire blank is alternatively or additionally provided on the outer side of the tire blank in the vulcanizing machine. To this end, a treatment chamber, which is referred to as a tire mold and can be opened or closed, is usually installed so that the tire blank to be vulcanized can be inserted, vulcanized and removed.
Following the general physical principle of the pressure propagation on all sides, the treatment chamber and/or the handling chamber or the tire mold has to support and absorb the pressing and pressure forces both in the radial and the axial direction. As a consequence of this, the movement devices for opening and closing the tire mold, regardless of whether the tire mold is arranged longitudinally or transversely to the rotational axis of the tire to be vulcanized, usually have to apply not only the forces for movement of at least one mold half but these also have to sufficiently dimensioned with regard to the closing forces during the tire vulcanization. On account of the closing forces which reach up to several kN, high-pressure fluid cylinders are used in most cases in addition to mechanical solutions such as toggle lever constructions or spindles.
Devices of this type certainly integrate both the movement function and the closing force function, but are axially very high in their construction and, depending on embodiment, are sensitive to radial forces and high temperatures or temperature gradients.
One approach for overcoming this complexity of problems can exist in separating the closing force function from the movement function in a device engineering manner. In the case of such a function separation, a locking function has to optionally be provided in addition, which locking function, under specified preconditions, can also be implemented within the movement device.
In order to create a suitable and advantageous closing force unit for the closing force function which is to be realized, isolated from the movement function, it is proposed to constructionally integrate into the tire vulcanizing machine especially linear drives, based on the plunger cylinder principle. To this end, at least one fluid cylinder is constructed as an integrative component part of the tire vulcanizing mold and/or of the machine components.
It is intended to introduce the fluid cylinder, which consists of a piston and possibly a piston rod and also a cylinder housing, not as a separate bought-in part but to build a fluid linear drive into the bottom plate or baseplate of the tire vulcanizing machine in an integrative manner.
The integrative style of construction can be implemented by the direct utilization of the bottom plate as a cylinder housing. To this end, holes are introduced into the bottom plate corresponding to the required number of fluid linear drives and which, depending on the embodiment of the fluid linear drive, can be constructed as a through-hole and/or as a blind hole. In this way, both piston-piston rod-linear drives and also piston-linear drives based on the plunger cylinder principle can be integrated.
If such a closing force unit is used for providing the closing force function, a movement device which implements the movement function has to be added in order to bring about the opening and closing of the tire mold or of the treatment chamber and therefore of the cavity of the tire vulcanizing machine.
Movement devices for providing the movement function can be constructed in an integrative or separate manner by means of a device, with a linear drive and a linear guide unit, which is decoupled from the closing force unit. Multifarious possibilities, such as fluid cylinders, electric linear drives, spindles and ball screw spindles or guides of a large variety of types lend themselves for this.
In the context of the function separation of closing force function and movement function, in many cases a further function object has to be achieved: The vertical position fixing of at least one of the treatment chamber-forming elements.
This fastening has to be carried out against the closing force and/or the pressure forces which result due to the treatment chamber internal pressure since in most cases the movement devices cannot, or cannot economically, be designed for this.